Disk drives are widely used in computers, consumer electronics and data processing systems for storing information in digital form. The disk drive typically includes one or more storage disks and one or more head suspension assemblies. Each head suspension assembly includes a slider having an air bearing surface, and a read/write head that transfers information to and from the storage disk. The rotation of the storage disk causes the slider to ride on an air bearing so that the read/write head is at a distance from the storage disk that is referred to as a “head-to-disk spacing” (also sometimes referred to herein as a “flying height”).
Because today's disk drives utilize storage disks having increasingly high densities of data tracks, decreasing the head-to-disk spacing has become of great importance. However, this desire for a very small head-to-disk spacing must be balanced with tribological concerns in order to avoid damage to the read/write head and/or the storage disk, as well as loss of data. Thus, the range between head-to-disk contact and a desirable head-to-disk spacing has become extremely small, requiring an increasingly more accurate control system.
During in-situ usage of the disk drive, the temperature of the slider typically varies. For example, during a write operation, the electrical resistance of the write element generates heat in and around the read/write head, resulting in thermal expansion of the write pole tips toward the storage disk. The situation is commonly referred to a write pole tip protrusion (“WPTP”). If the WPTP is too extensive, the slider can unintentionally contact the storage disk, causing off-track writing, damage to the slider or damage to the storage disk. However, during the manufacturing process, the temperature of the slider is normally lower than during in-situ usage. Further, the variation in head-to-disk spacing is usually not as pronounced during certain manufacturing processes as opposed to in-situ operation.